Base body for a component, projection exposure system and method for designing the base body

Abstract

The invention relates to a base body (30) for a component (M3) for semiconductor lithography, comprising at least one attachment (35) connected to the base body (30) in a connection area (32), wherein the connection area (32) has a decoupling geometry (40) for decoupling stresses and / or forces caused by the connection of the attachment (35). According to the invention, the base body is characterized in that the decoupling geometry (40) has at least one recess (33, 43, 43.1, 43.2) with a decoupling surface (38, 45). Furthermore, the invention relates to a method for designing a base body (30) for a component (M3) for semiconductor lithography with at least one attachment part (35) connected to the base body (30) in a connection area, wherein the connection area (32) has a decoupling geometry (40) for decoupling stresses and / or forces caused by the connection of the attachment part (35), comprising the following method steps: - Determination of the stresses and / or forces to be decoupled. - Determination of the parameters of the decoupling geometry (40) to define at least one recess (33,43,43.1,43.2) with a decoupling surface (38,45).

Description

[0001] The invention relates to a base body for a component, in particular a component for semiconductor lithography, a projection exposure system and a method for designing the base body.

[0002] Projection exposure systems for semiconductor lithography are used to create extremely fine structures, particularly on semiconductor devices or other microstructured components. The operating principle of these systems is based on creating extremely fine structures down to the nanometer range by means of a generally reduced-size image of structures on a mask, a so-called reticle, on an element to be structured, such as a wafer, which is coated with photosensitive material. The minimum dimensions of the created structures depend directly on the wavelength of the light used, the so-called useful light.The light sources used have wavelengths in an emission wavelength range known as the DUV range, from 100 nm to 300 nm. Recently, light sources with an emission wavelength in the range of a few nanometers, for example, between 1 nm and 120 nm, particularly in the range of 13.5 nm, have been increasingly used. This emission wavelength range is also referred to as the EUV range.

[0003] To illuminate the structures and, in particular, to image them, optical elements such as lenses and (especially in the field of EUV lithography) mirrors are used. Their so-called optical effective surfaces are exposed to useful light during normal operation of the associated system. Deviations of the optical effective surfaces from an optimal target position and shape have a significant impact on the quality of the image and thus on the quality of the manufactured components.

[0004] Typically, this problem is addressed by designing the optical elements used to be movable or deformable, allowing the aforementioned aberrations to be corrected during operation of the projection exposure system. The optical elements are usually arranged in receptacles for optical components, which are mounted on holders, which in turn can be movably mounted on a frame via actuators and can thus be positioned at a predetermined position.

[0005] Furthermore, various attachments, such as sensor reference surfaces or actuators, can be connected directly to a mirror, often using a screw connection, a clamp connection or an adhesive connection.

[0006] All joining techniques have the disadvantage that forces and / or stresses are introduced into the optical element, causing deformations in the material. These deformations can propagate through the element material to the effective optical surface, which can negatively impact image quality.

[0007] Where possible, the attachments are connected to the base body before the final production of the optical active surface, which allows for correction of any deformations caused. However, the deformations can change over time, particularly in the case of adhesives, which can cause new deformations. Therefore, the prior art provides for decoupling in the form of pins or cavities, as in German patent application DE 10 2012 209 309 A1. The pins can be designed as rods or as so-called ring pins. The decoupling effect of the pin is based on the ratio of the diameter of the adhesive surface to the length of the pin, which can, for example, be in the range of 1:1.5 to 1:3. The deformation already takes place in the area of ​​the pin, so that no or only a greatly reduced deformation is transferred to the actual optical element or the optical active surface.However, the cones have the disadvantage that they require additional installation space, which is not always available. Furthermore, the cones are usually designed as protruding structures machined from the solid material of the mirror. Thus, forming a mechanical structure requires comparatively expensive optical material, which negatively impacts manufacturing costs.

[0008] The cavities disclosed in the above-mentioned prior art are formed over the entire optical element and have the disadvantage that the decoupling depends on the location of the attachment part in relation to the extent of the cavity, so that the decoupling effect at the edge of the cavity can sometimes differ greatly from that in the center of the cavity.

[0009] The object of the present invention is to provide an optical element with a decoupling of connection points for add-on parts that eliminates the above-described disadvantages of the prior art. A further object is to provide a corresponding method.

[0010] These objects are achieved by a device and a method having the features of the independent claims. The subclaims relate to advantageous developments and variants of the invention.

[0011] A base body according to the invention for a component for semiconductor lithography has at least one attachment connected to the base body in a connection region. The connection region has a decoupling geometry for decoupling stresses and / or forces caused by the connection of the attachment. The decoupling geometry is characterized according to the invention in that it has at least one recess with a decoupling surface. The decoupling surface advantageously enables the deformation caused by the stresses and / or forces in the base body to propagate into the recess through a deformation of the decoupling surface. The deformation is thereby advantageously prevented from continuing further in the material in the direction of a functional surface of the component, thus stopping the deformation in the base body.

[0012] In one embodiment of the base body, the component can be embodied as an optical element of a semiconductor technology system. A semiconductor technology system can be, for example, a projection exposure system, a wafer inspection system, or a mask inspection or repair system. In these cases, the functional surface can be the optically active surface of an optical element corresponding to the system. The optical element can thus be embodied, for example, as a lens, a mirror, a diffractive optical element, or a mask.

[0013] In a first embodiment, the decoupling surface can be formed parallel to a functional surface of the base body that is to be decoupled. The decoupling surface delimits a recess formed as a cavity on one side, with the decoupling surface being formed on the side of the cavity facing away from the functional surface.

[0014] In the case of an optical element, the functional surface can be designed as an optical active surface, as already explained. Furthermore, the functional surface can also be designed as a reference surface used to determine the position of a component, for example, an interferometric arrangement. Deformation of the reference surface can lead to errors in the position determination and the resulting positioning of the component. The reference surface can be arranged either on the component itself or on a component designed as a reference frame, which can be used as a reference for determining the position of one or more components, for example, by a sensor.

[0015] In addition, the decoupling surface can be formed perpendicular to a functional surface of the base body that is to be decoupled. The vertical decoupling surface delimits a recess in the base body that is formed as an incision and / or a cavity, wherein the decoupling surface is formed on the surface of the recess facing the connecting surface. The vertical orientation of the decoupling surface can prevent a lateral continuation of the deformation in the material. This advantageously reduces or even completely prevents bypassing the decoupling surface formed parallel to the functional surface. The cavity can be produced, for example, using a subtractive manufacturing process, such as selective laser etching, or an additive manufacturing process, such as 3D printing.In the case of selective laser etching, a connection from the cavity to the surroundings of the base body is necessary, but this has no influence on the effect of the decoupling geometry.

[0016] In particular, the decoupling surface can have symmetrical subregions. The subregions can be defined by a reflection at a mirror plane or a rotation about a rotation axis, i.e., they can be mirror-imaged or rotationally symmetrical. A rotationally symmetrical design has the advantage of avoiding the stress peaks that frequently occur at edges and can also cause a local increase in deformation. In this case, any deformation that might extend to the functional surface would be comparatively flat. The flatter and longer-wavelength the deformations, the smaller their impact on the image quality and the easier they can be compensated for, for example, by other optical elements.

[0017] Furthermore, a node point can be formed at the intersection of at least two decoupling surfaces. Within the meaning of the invention, the node point is not a geometric point, but can have a lateral extension that can extend up to a closed ring. The node point determines, on the one hand, the decoupling effect of the decoupling geometry and, on the other hand, its rigidity. The arrangement and design of the node point by the decoupling surfaces can be adjusted during the design of the decoupling geometry according to the predetermined decoupling effect and rigidity.

[0018] In particular, the node point can be formed in the neutral plane of the base body. The neutral plane is the plane which has zero stress, at least in the area of ​​the connection between the attachment and the base body. A shrinkage of the material caused by the shrinkage of an adhesive generates a compressive stress in the material, which, upon elastic deformation, generates a tensile stress of the same magnitude on the functional surface or the decoupling surface. The neutral plane is therefore the plane in which the compressive stresses transform into tensile stresses. The arrangement of the node point in the neutral plane has the advantage that a decoupling plane is also formed vertically above the node point, into which the deformation can propagate.

[0019] In a further embodiment, the base body can have at least two independent connection areas. This has the advantage that the decoupling geometry of the connection areas can be adapted according to the predetermined boundary conditions. For example, a decoupling geometry at the edge of the base body can have different properties than in the center of the base body.

[0020] In particular, one attachment can be connected to the base body for each connection area. This advantageously allows for individual adaptation of the decoupling geometry, so that, for example, the decoupling geometry can be adapted to different attachments and the associated different stresses and / or forces. In general, if more than one decoupling geometry is present, the properties can be adapted to the respective predetermined boundary conditions.

[0021] A projection exposure system according to the invention for semiconductor lithography has a base body according to one of the embodiments explained above.

[0022] A method according to the invention for designing a base body for a component for semiconductor lithography with at least one attachment connected to the base body in a connection region, wherein the connection region has a decoupling geometry for decoupling stresses and / or forces caused by the connection of the attachment, comprises the following method steps: - Determination of the stresses and / or forces to be decoupled. - Determination of the parameters of the decoupling geometry to define at least one recess with a decoupling surface.

[0023] The method makes it possible to arrange the at least one recess in such a way that the deformations propagated to the functional surface are advantageously reduced. The shape of the remaining deformations can also play a role as a design parameter, as explained above.

[0024] Furthermore, the size of the decoupling area can be determined as a parameter of the recess. The larger the decoupling area, the greater the decoupling effect of the connection in the vertical direction can be.

[0025] In addition, the vertical position of the decoupling surface in the base body can be determined as another parameter of the recess. This influences both the vertical and lateral stiffness of the connection, which also affects the decoupling effect. The vertical position of the recess can vary depending on the other design parameters.

[0026] In a further embodiment, the number of decoupling surfaces can be determined as a further parameter. Each recess can have at least one decoupling surface, whereby a recess can also have more than one decoupling surface. Depending on the size and type of the specific stresses and / or forces, the number of decoupling surfaces can be advantageously adjusted.

[0027] Furthermore, the orientation of the decoupling surfaces can be determined as a further parameter. As described above, the decoupling surface can be parallel and / or vertical, although decoupling surfaces with any orientation to the functional surface of the component are also conceivable.

[0028] In particular, the position of the node formed at the intersection of at least two decoupling surfaces can be determined, wherein the arrangement in the neutral fiber, as already explained above, can be particularly advantageous.

[0029] The size, number and distribution of the adhesive surfaces for connecting the add-on parts to the base body influence the stresses and / or forces introduced into the base body and, in addition to the design of the base body, in particular the decoupling geometry, can contribute to a reduction of deformations on the functional surface of the component.

[0030] In the following, embodiments and variants of the invention are explained in more detail with reference to the drawings. Fig. 1 schematically shows in meridional section a projection exposure system for EUV projection lithography, Fig. 2 schematically shows in meridional section a projection exposure system for DUV projection lithography, Fig. 3 a schematic representation of a base body with a connection area according to the invention, Fig. 4 a schematic sectional view of a connection area according to the invention, Fig. 5 shows a further embodiment of the invention, and Fig. 6 a flowchart of a method according to the invention.

[0031] In the following, with reference to the Fig. 1 describes, by way of example, the essential components of a projection exposure system 1 for microlithography. The description of the basic structure of the projection exposure system 1 and its components is not intended to be limiting.

[0032] One embodiment of an illumination system 2 of the projection exposure system 1 has, in addition to a radiation source 3, an illumination optics 4 for illuminating an object field 5 in an object plane 6. In an alternative embodiment, the light source 3 can also be provided as a separate module from the rest of the illumination system. In this case, the illumination system does not include the light source 3.

[0033] A reticle 7 arranged in the object field 5 is illuminated. The reticle 7 is held by a reticle holder 8. The reticle holder 8 can be displaced, in particular in a scanning direction, via a reticle displacement drive 9.

[0034] In the Fig. 1 shows a Cartesian xyz coordinate system for explanation. The x-direction is perpendicular to the plane of the drawing. The y-direction is horizontal and the z-direction is vertical. The scanning direction is in the Fig. 1 along the y-direction. The z-direction runs perpendicular to the object plane 6.

[0035] The projection exposure system 1 comprises a projection optics 10. The projection optics 10 serves to image the object field 5 into an image field 11 in an image plane 12. The image plane 12 runs parallel to the object plane 6. Alternatively, an angle other than 0° between the object plane 6 and the image plane 12 is also possible.

[0036] A structure on the reticle 7 is imaged onto a light-sensitive layer of a wafer 13 arranged in the image plane 12 in the region of the image field 11. The wafer 13 is held by a wafer holder 14. The wafer holder 14 can be displaced, in particular along the y-direction, via a wafer displacement drive 15. The displacement of the reticle 7, on the one hand, via the reticle displacement drive 9, and the displacement of the wafer 13, on the other hand, via the wafer displacement drive 15, can be synchronized with each other.

[0037] The radiation source 3 is an EUV radiation source. The radiation source 3 emits, in particular, EUV radiation 16, which is also referred to below as useful radiation, illumination radiation, or illumination light. The useful radiation has, in particular, a wavelength in the range between 5 nm and 30 nm. The radiation source 3 can be a plasma source, for example, an LPP source (laser produced plasma) or a DPP source (gas discharged produced plasma). It can also be a synchrotron-based radiation source. The radiation source 3 can be a free-electron laser (FEL).

[0038] The illumination radiation 16 emanating from the radiation source 3 is focused by a collector 17. The collector 17 can be a collector with one or more ellipsoidal and / or hyperboloidal reflection surfaces. The at least one reflection surface of the collector 17 can be exposed to the illumination radiation 16 at grazing incidence (GI), i.e., at angles of incidence greater than 45° relative to the normal direction of the mirror surface, or at normal incidence (NI), i.e., at angles of incidence less than 45°. The collector 17 can be structured and / or coated, on the one hand, to optimize its reflectivity for the useful radiation and, on the other hand, to suppress stray light.

[0039] After the collector 17, the illumination radiation 16 propagates through an intermediate focus in an intermediate focal plane 18. The intermediate focal plane 18 can represent a separation between a radiation source module, comprising the radiation source 3 and the collector 17, and the illumination optics 4.

[0040] The illumination optics 4 comprises a deflecting mirror 19 and, downstream of this in the beam path, a first facet mirror 20. The deflecting mirror 19 can be a flat deflecting mirror or, alternatively, a mirror with a beam-influencing effect beyond the pure deflection effect. Alternatively or additionally, the deflecting mirror 19 can be designed as a spectral filter that separates a useful light wavelength of the illumination radiation 16 from stray light of a different wavelength. If the first facet mirror 20 is arranged in a plane of the illumination optics 4 that is optically conjugated to the object plane 6 as the field plane, it is also referred to as a field facet mirror. The first facet mirror 20 comprises a plurality of individual first facets 21, which are also referred to below as field facets. Of these facets 21, Fig. 1 only some examples are shown.

[0041] The first facets 21 can be designed as macroscopic facets, in particular as rectangular facets or as facets with an arcuate or partially circular edge contour. The first facets 21 can be designed as flat facets or, alternatively, as convexly or concavely curved facets.

[0042] As is known, for example, from DE 10 2008 009 600 A1, the first facets 21 themselves can also be composed of a plurality of individual mirrors, in particular a plurality of micromirrors. The first facet mirror 20 can, in particular, be designed as a microelectromechanical system (MEMS system). For details, reference is made to DE 10 2008 009 600 A1.

[0043] Between the collector 17 and the deflecting mirror 19, the illumination radiation 16 runs horizontally, i.e. along the y-direction.

[0044] In the beam path of the illumination optics 4, a second facet mirror 22 is arranged downstream of the first facet mirror 20. If the second facet mirror 22 is arranged in a pupil plane of the illumination optics 4, it is also referred to as a pupil facet mirror. The second facet mirror 22 can also be arranged at a distance from a pupil plane of the illumination optics 4. In this case, the combination of the first facet mirror 20 and the second facet mirror 22 is also referred to as a specular reflector. Specular reflectors are known from US 2006 / 0132747 A1, EP 1 614 008 B1, and US Pat. No. 6,573,978.

[0045] The second facet mirror 22 comprises a plurality of second facets 23. In the case of a pupil facet mirror, the second facets 23 are also referred to as pupil facets.

[0046] The second facets 23 can also be macroscopic facets, which can, for example, be round, rectangular, or hexagonal, or alternatively facets composed of micromirrors. Reference is also made to DE 10 2008 009 600 A1 in this regard.

[0047] The second facets 23 can have planar or alternatively convex or concave curved reflection surfaces.

[0048] The illumination optics 4 thus form a double-faceted system. This basic principle is also known as a honeycomb condenser (fly's eye integrator).

[0049] It may be advantageous to arrange the second facet mirror 22 not exactly in a plane that is optically conjugated to a pupil plane of the projection optics 10. In particular, the pupil facet mirror 22 can be arranged tilted relative to a pupil plane of the projection optics 10, as described, for example, in DE 10 2017 220 586 A1.

[0050] With the help of the second facet mirror 22, the individual first facets 21 are imaged into the object field 5. The second facet mirror 22 is the last beam-forming mirror or actually the last mirror for the illumination radiation 16 in the beam path before the object field 5.

[0051] In a further embodiment of the illumination optics 4 (not shown), a transmission optics can be arranged in the beam path between the second facet mirror 22 and the object field 5, which transmission optics contributes in particular to the imaging of the first facets 21 into the object field 5. The transmission optics can have exactly one mirror, but alternatively also two or more mirrors, which are arranged one behind the other in the beam path of the illumination optics 4. The transmission optics can in particular comprise one or two mirrors for normal incidence (NI mirrors, normal incidence mirrors) and / or one or two mirrors for grazing incidence (GI mirrors, grazing incidence mirrors).

[0052] The illumination optics 4 has in the version shown in the Fig. 1, after the collector 17 there are exactly three mirrors, namely the deflection mirror 19, the field facet mirror 20 and the pupil facet mirror 22.

[0053] In a further embodiment of the illumination optics 4, the deflection mirror 19 can also be omitted, so that the illumination optics 4 can then have exactly two mirrors after the collector 17, namely the first facet mirror 20 and the second facet mirror 22.

[0054] The imaging of the first facets 21 by means of the second facets 23 or with the second facets 23 and a transmission optics into the object plane 6 is usually only an approximate imaging.

[0055] The projection optics 10 comprises a plurality of mirrors Mi, which are numbered according to their arrangement in the beam path of the projection exposure system 1.

[0056] In the Fig. In the example shown in Figure 1, the projection optics 10 comprises six mirrors M1 to M6. Alternatives with four, eight, ten, twelve, or a different number of mirrors M1 are also possible. The penultimate mirror M5 and the last mirror M6 each have a passage opening for the illumination radiation 16. The projection optics 10 is a doubly obscured optic. The projection optics 10 has an image-side numerical aperture that is greater than 0.5 and can also be greater than 0.6, for example, 0.7 or 0.75.

[0057] Reflection surfaces of the mirrors Mi can be designed as freeform surfaces without a rotational symmetry axis. Alternatively, the reflection surfaces of the mirrors Mi can be designed as aspherical surfaces with exactly one rotational symmetry axis of the reflection surface shape. The mirrors Mi, like the mirrors of the illumination optics 4, can have highly reflective coatings for the illumination radiation 16. These coatings can be designed as multilayer coatings, in particular with alternating layers of molybdenum and silicon.

[0058] The projection optics 10 has a large object-image offset in the y-direction between a y-coordinate of a center of the object field 5 and a y-coordinate of the center of the image field 11. This object-image offset in the y-direction can be approximately as large as a z-distance between the object plane 6 and the image plane 12.

[0059] The projection optics 10 can, in particular, be anamorphic. It has, in particular, different magnifications βx, βy in the x- and y-directions. The two magnifications βx, βy of the projection optics 10 are preferably (βx, βy) = (+ / - 0.25, + / - 0.125). A positive magnification β means imaging without image inversion. A negative sign for the magnification β means imaging with image inversion.

[0060] The projection optics 10 thus leads to a reduction in the ratio 4:1 in the x-direction, i.e. in the direction perpendicular to the scanning direction.

[0061] The projection optics 10 results in a reduction of 8:1 in the y-direction, i.e. in the scanning direction.

[0062] Other magnifications are also possible. Magnifications with the same sign and absolutely identical in the x and y directions, for example, with absolute values ​​of 0.125 or 0.25, are also possible.

[0063] The number of intermediate image planes in the x- and y-directions in the beam path between the object field 5 and the image field 11 can be the same or can vary depending on the design of the projection optics 10. Examples of projection optics with different numbers of such intermediate images in the x- and y-directions are known from US 2018 / 0074303 A1.

[0064] Each of the pupil facets 23 is assigned to exactly one of the field facets 21 to form a respective illumination channel for illuminating the object field 5. This can, in particular, result in illumination according to the Köhler principle. The far field is divided into a plurality of object fields 5 using the field facets 21. The field facets 21 generate a plurality of images of the intermediate focus on the pupil facets 23 assigned to them.

[0065] The field facets 21 are each imaged onto the reticle 7 by an associated pupil facet 23, superimposed on one another, to illuminate the object field 5. The illumination of the object field 5 is, in particular, as homogeneous as possible. It preferably has a uniformity error of less than 2%. Field uniformity can be achieved by superimposing different illumination channels.

[0066] By arranging the pupil facets, the illumination of the entrance pupil of the projection optics 10 can be geometrically defined. By selecting the illumination channels, in particular the subset of the pupil facets that guide light, the intensity distribution in the entrance pupil of the projection optics 10 can be adjusted. This intensity distribution is also referred to as the illumination setting.

[0067] A likewise preferred pupil uniformity in the area of ​​defined illuminated sections of an illumination pupil of the illumination optics 4 can be achieved by redistributing the illumination channels.

[0068] Further aspects and details of the illumination of the object field 5 and in particular of the entrance pupil of the projection optics 10 are described below.

[0069] The projection optics 10 can, in particular, have a homocentric entrance pupil. This can be accessible. It can also be inaccessible.

[0070] The entrance pupil of the projection optics 10 cannot usually be precisely illuminated with the pupil facet mirror 22. When the projection optics 10 images the center of the pupil facet mirror 22 telecentrically onto the wafer 13, the aperture rays often do not intersect at a single point. However, a surface can be found in which the pairwise determined distance of the aperture rays is minimized. This surface represents the entrance pupil or a surface conjugate to it in spatial space. In particular, this surface exhibits a finite curvature.

[0071] It is possible that the projection optics 10 have different entrance pupil positions for the tangential and sagittal beam paths. In this case, an imaging element, in particular an optical component of the transmission optics, should be provided between the second facet mirror 22 and the reticle 7. With the help of this optical element, the different positions of the tangential entrance pupil and the sagittal entrance pupil can be taken into account.

[0072] In the Fig. In the arrangement of the components of the illumination optics 4 shown in Figure 1, the pupil facet mirror 22 is arranged in a surface conjugated to the entrance pupil of the projection optics 10. The field facet mirror 20 is arranged tilted relative to the object plane 6. The first facet mirror 20 is arranged tilted relative to an arrangement plane defined by the deflection mirror 19.

[0073] The first facet mirror 20 is arranged tilted to an arrangement plane which is defined by the second facet mirror 22.

[0074] Fig. 2 shows a schematic meridional section of another projection exposure system 101 for DUV projection lithography, in which the invention can also be used.

[0075] The structure of the projection exposure system 101 and the principle of imaging is comparable to that in Fig. 1 described structure and procedure. Identical components are provided with a 100 Fig. 1 raised reference numerals, the reference numerals in Fig. So 2 start with 101.

[0076] In contrast to a Fig. 1, due to the longer wavelength of the DUV radiation 116 used as useful light in the range from 100 nm to 300 nm, in particular from 193 nm, refractive, diffractive and / or reflective optical elements 117, such as lenses, mirrors, prisms, cover plates and the like, can be used in the DUV projection exposure system 101 for imaging or for illumination.The projection exposure system 101 essentially comprises an illumination system 102, a reticle holder 108 for receiving and precisely positioning a reticle 107 provided with a structure, by means of which the later structures on a wafer 113 are determined, a wafer holder 114 for holding, moving and precisely positioning this wafer 113 and a projection lens 110 with a plurality of optical elements 117, which are held via mounts 118 in a lens housing 119 of the projection lens 110.

[0077] The illumination system 102 provides DUV radiation 116 required for imaging the reticle 107 on the wafer 113. A laser, a plasma source, or the like can be used as the source for this radiation 116. The radiation 116 is shaped in the illumination system 102 via optical elements such that the DUV radiation 116, upon impinging on the reticle 107, exhibits the desired properties with regard to diameter, polarization, wavefront shape, and the like.

[0078] The structure of the subsequent projection optics 101 with the lens housing 119 does not differ in principle from that in Fig. 1 and is therefore not described further.

[0079] Fig. 3 shows a schematic representation of a base body 30 of an optical element, such as a mirror M3 of the Fig. 1, with seven connection areas 32 for connecting add-on parts (not shown) to the base body 30.

[0080] The base body 30, shown in a view from below, has an optical active surface 31, i.e. the surface which is exposed to useful light in order to image the structures of the mask onto the wafer.

[0081] The connection areas 32 are formed on the rear side 37 of the base body 30 opposite the optical active surface 31. Furthermore, each connection area 32 has a decoupling geometry 40 ( Fig. 4) with a recess formed in the base body 30 as a cavity 33, which in the example shown is circular and in the Fig. 4 is explained in more detail.

[0082] In the illustrated embodiment, the adhesive connection comprises six adhesive surfaces designed as so-called adhesive pads 34, which are arranged in the center of the cavity 33. The implementation of the adhesive connection using multiple adhesive pads 34 is based on the fact that the influence of the diameter of the adhesive pad 34 on the stresses and / or forces introduced into the base body 30 and on the rigidity of the connection by the adhesive pad 34 are not proportional to one another. This makes it advantageous to use multiple small adhesive pads 34 instead of one large adhesive pad, which causes less deformation on the optical active surface 31 while maintaining the same rigidity.

[0083] Fig. 4 shows a sectional view through a connection area 32 of a base body 30. The decoupling geometry 40 has the cavity 33, a cheek area 41 and a bottom area 42, wherein the formation of these three areas 33, 41, 42 significantly influences the decoupling effect of the connection area 40.

[0084] To explain the functionality of the decoupling geometry 40, the Fig. 4, only one adhesive pad 34 is shown. This connects an attachment 35, which in turn can be connected to further elements 36, such as a support frame or an actuator, to the base body 30. The adhesive pads 34 contract upon curing and / or when the ambient humidity decreases. The resulting stresses are transferred to the base body 30, causing it to also contract in the area of ​​the adhesive pad 34, generating compressive stresses in the base body.

[0085] This deformation continues in the material and leads to tensile stresses and a bulging of the material at a decoupling surface 38 of the base region 42, which delimits the cavity 33 in the direction of the rear side 37 of the base body 30. The decoupling surface 38 can expand freely through the cavity 33 above it, whereby further continuation of the deformations in the material is advantageously reduced or even completely interrupted. This has the advantage that the optical active surface 31 is not deformed, which in turn has a positive effect on the imaging quality of the projection exposure system 1 ( Fig. 1) affects.

[0086] Furthermore, the cheek area 41 is also pulled in the direction of the adhesive pad 34, which is achieved by the Fig. 4 dashed and diagonal lines at the edge of the connection area 32. The resulting moment is transmitted through the material in the direction of the optical effective surface 31 and leads there to a bulge, which is shown in the form of a dashed line in the Fig. 4 is shown.

[0087] The decoupling geometry 40 is determined such that, on the one hand, the deformations caused by the adhesive pads 34 in the area of ​​the optical effective surface 31 are within the permissible deviations from the desired geometry of the optical effective surface. On the other hand, the rigidity of the connection or the decoupling geometry 40 must be within the predetermined requirements, which can ensure, for example, the controllability of the optical element 30.

[0088] To optimize these requirements, three parameters are H , d K , h Bcrucial which in the Fig. 4 are shown with solid double arrows.

[0089] A first parameter is the diameter d H of the cavity 33, which can be varied. As a first approximation, a larger diameter d H to a softer connection, which reduces the stiffness in the vertical direction and increases the decoupling effect. The diameter d H of the cavity 33 is in the range of 80 to 120 mm in the example shown.

[0090] Another parameter is the diameter d Kof the adhesive pad 34. A smaller diameter leads to a lower introduction of stresses and / or forces and thus to a reduction in deformation. At the same time, the stiffness of the connection is reduced. Since the ratio of the reduction in stiffness to the reduction in stresses and / or forces is not proportional to each other, the adhesive connection, as shown in the Fig. 3, can be realized by several small adhesive pads 34. The diameter of the adhesive pads 34 in the example shown is in a range of 3 mm to 10 mm.

[0091] A third parameter is the height h B of the base region 42 of the decoupling geometry 40, which corresponds to the distance of the cavity 33 from the rear side 37 of the base body 30. The higher the base region 42, the stiffer it is, whereby this applies both to the vertical z-direction, i.e., perpendicular to the optical effective surface 31, and to the lateral direction. The height hB This influences, on the one hand, the deformation of the base 42 in the vertical direction and, on the other hand, the deformations in the lateral direction that continue to the cheek regions 41. The stiffer the base 42, the more stresses and / or forces are transferred to the cheek regions 41 and thus, as explained above, lead to a deformation of the optical effective surface 31. The height h B of the base area 42 is in the example shown in the range from 8mm to 30mm.

[0092] Fig. Figure 5 shows a further embodiment of the invention, wherein the decoupling geometry 40 is different from that shown in Fig. 4, has additional incisions 43, 43.1, 43.2. The incisions 43 separate the bottom region 42 from the cheek region 41 of the decoupling geometry 40, whereby a lateral decoupling surface 45 is formed on the bottom region 42. This can deform freely, thereby preventing the continuation of the deformation in the material over the cheek region 41, as shown in the Fig. 4, can be advantageously reduced or completely prevented. The incision 43 thus has the effect of decoupling the lateral contraction of the base region 42 from the cheek region 41 caused by the tensions and / or forces of the adhesive pad 34.

[0093] Between the cavity 33 and the incisions 43, 43.1, 43.2, a junction point 44.1, 44.2 is formed. Depending on the arrangement and design of the cavity 33 and the incisions 43, 43.1, 43.2, the junction point 44.1, 44.2 can be formed vertically and / or laterally within the base body 30. While on the left side of the Fig. 5 the incision 43 is formed exclusively from the rear side 37 of the base body 30 in the direction of the cavity 33, the right side of the Fig. 5 two incisions 43.1, 43.2. A first incision 43.1 opens toward the rear side 37 of the base body 30, and a second incision 43.2 opens toward the decoupling surface 38 of the cavity 33. This allows the node 44.2 to be formed in the neutral fiber of the base body 30, at which the material of the base body 30 exhibits neither compressive stresses due to the contraction of the rear side 37 of the base body nor tensile stresses due to the bulging of the decoupling surface 38 of the base region 42. As a result, no stresses and therefore no deformations propagate beyond the node 44.2 toward the optical effective surface 31.

[0094] The design of the cuts 43, 43.1, 43.2 can thus be used as a further parameter for optimizing the connection area 32 in order to ensure, on the one hand, the decoupling of the stresses and / or forces and, on the other hand, the rigidity of the connection within the predetermined requirements.

[0095] Fig. 6 describes a possible method for designing a base body 30 with at least one recess 33, 43, 43.1, 43.2 and a decoupling surface 38, 45, as shown in the preceding figures ( Fig. 3 to Fig. 5) was described.

[0096] In a first method step 51, the stresses and / or forces to be decoupled are determined. These are caused by the connection of the attachment 35 to the base body 30. The parameters influencing the stresses and / or forces are the diameter of the bonding surface, the thickness of the bonding gap, the type of adhesive, and the ambient conditions as the parameters for determination.

[0097] In a second method step 52, the parameters of the decoupling geometry 40 ( Fig. 4, Fig.5) to define at least one recess 33, 43, 43.1, 43.2 with a decoupling surface 38, 45. This can be determined, for example, using FE models in which the parameters mentioned above (diameter of recess 33, thickness of base area 41, arrangement of nodes 44.1, 44.2) are varied. The resulting decoupling geometry advantageously reduces the deformation of the optical effective surface 31 or even completely prevents its deformation. List of reference symbols 1 projection exposure system 2 Lighting system 3 Radiation source 4 Lighting optics 5 Object field 6 Object level 7 reticles 8 reticle holders 9 Reticle displacement drive 10 Projection optics 11 Image field 12 Image plane 13 wafers 14 wafer holders 15 Wafer relocation drive 16 EUV radiation 17 Collector 18 Intermediate focal plane 19 Deflecting mirrors 20 facet mirrors 21 facets 22 facet mirrors 23 facets 30 basic bodies 31 optical effective area 32 connection area 33 Recess 34 adhesive pad 35 Attachment 36 Additional element 37 Back of base body 38 Deformation surface cavity 40 Decoupling geometry 41 Cheek area 42 floor area 43, 43.1, 43.2 incision 44.1, 44.2 Intersection of deformation surfaces 45 Deformation surface incision 51 Process step 1 52 Process step 2 101 Projection exposure system 102 Lighting system 107 reticles 108 reticle holders 110 Projection optics 113 wafers 114 wafer holders 116 DUV radiation 117 optical element 118 versions 119 lens housings M1-M6 mirrors d H Width cavity h B Thickness floor area d K Diameter of adhesive surface QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2012 209 309 A1

[0007] DE 10 2008 009 600 A1 [0042, 0046] US 2006 / 0132747 A1

[0044] EP 1 614 008 B1

[0044] US 6,573,978

[0044] DE 10 2017 220 586 A1

[0049] US 2018 / 0074303 A1

[0063]

Claims

[1] Base body (30) for a component (M3) for semiconductor lithography with at least one attachment (35) connected to the base body (30) in a connection area (32), wherein the connection area (32) has a decoupling geometry (40) for decoupling stresses and / or forces caused by the connection of the attachment (35), characterized by that the decoupling geometry (40) has at least one recess (33,43,43.1,43.2) with a decoupling surface (38,45). [2] Base body (30) according to claim 1, characterized by that the component (M3) is designed as an optical element of a semiconductor technology system (1,101). [3] Base body (30) according to one of claims 1 or 2, characterized by that the decoupling surface (38,45) is formed parallel to a functional surface (31) of the base body (30) to be decoupled. [4] Base body (30) according to one of the preceding claims, characterized bythat the decoupling surface (38,45) is formed perpendicular to a functional surface (31) of the base body (30) to be decoupled. [5] Base body (30) according to one of the preceding claims, characterized by that the decoupling surface (38,45) has symmetrical sub-areas. [6] Base body (30) according to one of the preceding claims, characterized by that a node point (44.1,44.2) is formed at the intersection point of at least two decoupling surfaces (38,45). [7] Base body (30) according to claim 6, characterized by that the node point (44.2) is formed in the neutral plane of the base body (30). [8] Base body (30) according to one of claims 4 to 7, characterized by that the functional surface is designed as an optical active surface (31). [9] Base body (30) according to one of claims 4 to 7, characterized by that the functional surface is designed as a reference surface for determining the position of the component (M3). [10] Base body (30) according to one of the preceding claims, characterized by that the base body (30) has at least two independent connection areas (32). [11] Base body (30) according to one of the preceding claims, characterized by that for each connection area (32) an attachment part (35) is connected to the base body (30). [12] Projection exposure system (1,101) for semiconductor lithography with a base body (30) according to one of the preceding claims. [13] Method for designing a base body (30) for a component (M3) for semiconductor lithography with at least one attachment (35) connected to the base body (30) in a connection region, wherein the connection region (32) has a decoupling geometry (40) for decoupling stresses and / or forces caused by the connection of the attachment (35), comprising the following method steps: - Determination of the stresses and / or forces to be decoupled. - Determining the parameters of the decoupling geometry (40) for defining at least one recess (33,43,43.1,43.2) with a decoupling surface (38,45). [14] Method according to claim 13, characterized by that as a parameter of the recess (33,43,43.1,43.2) the size (d H ) of the decoupling surface (38,45) is determined. [15] Method according to one of claims 13 or 14, characterized by that the vertical position of the decoupling surface (38,45) in the base body (30) is determined as a further parameter of the decoupling surface (38,45). [16] Method according to one of claims 13 to 15, characterized by that the number of decoupling surfaces (38,45) is determined as a further parameter. [17] Method according to one of claims 13 to 16, characterized by that the orientation of the decoupling surfaces (38,45) is determined as a further parameter. [18] Method according to one of claims 13 to 17, characterized by that the position of a node point (44.1,44.2) formed at the intersection of at least two decoupling surfaces (38,45) is determined.

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